Antegrade cold blood cardioplegia is not demonstrably advantageous over cold crystalloid cardioplegia in surgery for congenital heart disease

Cardioplegia in Open Heart Surgery: Age Matters

INTRODUCTION

Cardioplegia is a pharmacological approach essential for the protection of the heart from ischemia-reperfusion (I-R) injury. Over the years, numerous cardioplegic solutions have been developed, with each cardioplegic approach having its advantages and disadvantages. Cardioplegic solutions can be divided into crystalloid and blood cardioplegic solutions, and an experienced surgeon chooses the type of solution based on the individual needs of patients in order to provide optimal heart protection. Importantly, the pediatric immature myocardium is structurally, physiologically, and metabolically different from the adult heart, and consequently its needs to achieve cardioplegic arrest strongly differ. Therefore, the present review aimed to provide a summary of the cardioplegic solutions available to pediatric patients with a special focus on emphasizing differences in heart injury after various cardioplegic solutions, the dosing strategies, and regimens.

MATERIAL AND METHODS

The PubMed database was searched using the terms cardioplegia, I-R, and pediatric population, and studies that investigated the influence of cardioplegic strategies on markers of cardiac muscle damage were further analyzed in this review.

CONCLUSIONS

A large body of evidence suggested more prominent benefits achieved with blood compared to those with crystalloid cardioplegia in pediatric myocardium preservation. However, standardized and uniform protocols have not been established so far, and an experienced surgeon chooses the type of cardioplegia solution based on the individual needs of patients, while the severity of myocardial damage strongly depends on the type and duration of the surgical procedure, overall patient condition, and presence of comorbidities, etc.

Comparison between blood and non-blood cardioplegia in tetralogy of Fallot

BACKGROUND

Cardioplegia is an integral part of myocardial protection. The superiority of blood cardioplegia in adult patients has been reported. However, this is yet to be studied in cyanotic pediatric patients.

METHODS

A randomized open-label trial was conducted in 70 patients with tetralogy of Fallot. They were divided into two groups: 35 patients had crystalloid cardioplegia (controls), and 35 had blood cardioplegia. Lactate and coronary oxygen extraction in arterial blood and the coronary sinus were measured immediately after cessation of cardiopulmonary bypass, 15 and 30 min later. Postoperative mortality, major adverse cardiac events, mechanical ventilation time, inotrope administration, arrhythmias, right ventricular function, intensive care unit and hospital length of stay were observed.

RESULTS

There were no significant differences in clinical outcomes or lactate levels. There was a significant difference in coronary oxygen extraction immediately and 15 min after cessation of cardiopulmonary bypass ( p = 0.038, p = 0.015).

CONCLUSION

Blood cardioplegia gave a better postoperative oxygen extraction value but there were no differences in myocardial damage or clinical outcome between the two groups.

Type of cardioplegic solution as a factor influencing the clinical outcome of open-heart congenital procedures

Introduction

Cardioplegia is one of the most important modalities of myocardial protection during heart surgery.

Aim

To assess the impact of blood cardioplegia on postoperative variables, in comparison with two types of crystalloid cardioplegic solutions during pediatric heart surgery.

Material and methods

One thousand one hundred and twenty-nine patients underwent surgical correction of congenital heart disease with cardioplegia administration between 2006 and 2012. Nonlinear regression models of postoperative low cardiac output syndrome (LCOS) incidence, catecholamine index and total complication count were developed using a genetic algorithm. The Akaike information criterion was applied for selection of the best model. The following explanatory variables were evaluated: cardioplegia type (ST - Saint Thomas, n = 440; FR - Fresenius, n = 432; BL - Calafiore, n = 257), congenital heart diseases (CHD) type, age, sex, genetic disorder presence, body surface area (BSA), cardiopulmonary bypass (CBP) time, aortic cross-clamp time, operation urgency, redo surgery, surgeon.

Results

Low cardiac output syndrome presence and higher than average catecholamine indexes were negatively influenced by use of crystalloid cardioplegia (ST or FR), presence of specific CHDs, redo surgery and prolonged CBP time. Increased complication count was related to: crystalloid cardioplegia, presence of specific CHDs, redo surgery, urgency of operation, operation time and CBP time. Higher BSA had a protective effect against higher catecholamine index and increased complication count. Older age was protective against LCOS.

Conclusions

Cardioplegic solutions type influences postoperative variables in children after heart surgery by the negative impact of crystalloid cardioplegia. Blood cardioplegia presents potential advantages for patients - its application may reduce the incidence of low cardiac output syndrome and related complications.

Cold crystalloid versus warm blood cardioplegia in patients undergoing aortic valve replacement

Background

Myocardial protection techniques during cardiac arrest have been extensively investigated in the clinical setting of coronary revascularization. Fewer studies have been carried out of patients affected by left ventricular hypertrophy, where the choice of type and temperature of cardioplegia remain controversial. We have retrospectively investigated myocardial injury and short-term outcome in patients undergoing aortic valve replacement plus or minus coronary artery bypass grafting with using cold crystalloid cardioplegia (CCC) or warm blood cardioplegia (WBC).

Methods

From January 2015 to October 2016, 191 consecutive patients underwent aortic valve replacement plus or minus coronary artery bypass grafting in normothermic cardiopulmonary bypass. Cardiac arrest was obtained with use of intermittent antegrade CCC group (n=32) or WBC group (n=159), according with the choice of the surgeon.

Results

As compared with WBC group, in CCC group creatine-kinase-MB (CK-MB), cardiac troponin I (cTnI), aspartate aminotransferase (AST) release, and their peak levels, were lower during each time points of evaluation, with the greater statistically significant difference at time 0 (P<0.05, for all comparisons). A time 0, CK-MB/CK ratio >10% was 5.9% in CCC group versus 7.8% in WBC group (P<0.0001). At time 0 CK-MB/CK ratio >10% in patients undergoing isolated aortic valve replacement was 6.0% in CCC group versus 8.0% in WBC group (P<0.01). No any difference was found in perioperative myocardial infarction (0% versus 3.8%), postoperative (PO) major complications (15.6% versus 16.4%), in-hospital mortality (3.1% versus 1.3%).

Conclusions

In aortic valve surgery a significant decrease of myocardial enzymes release is observed in favor of CCC, but this difference does not translate into different clinical outcome. However, this study suggests that in presence of cardiac surgical conditions associated with significant left ventricular hypertrophy, i.e., the aortic valve disease, a better myocardial protection can be achieved with the use of a cold rather than a warm cardioplegia. Therefore, CCC can be still safely used.

Blood Versus Crystalloid Cardioplegia in Pediatric Cardiac Surgery: A Systematic Review and Meta-analysis

The benefit of blood cardioplegia (BCP) compared to crystalloid cardioplegia (CCP) is still debatable. Our aim was to systematically review and synthesize all available evidence on the use of BCP and CCP to assess if any modality provides superior outcomes in pediatric cardiac surgery. A systematic literature search of the PubMed and Cochrane databases was performed with respect to the PRISMA statement (end-of-search date: January 30th, 2017). We extracted data on study design, demographics, cardioplegia regimens, and perioperative outcomes as well as relevant biochemical markers, namely cardiac troponin I (cTnI), lactate, and ATP levels at baseline, after reperfusion and postoperatively at 1, 4, 12, and 24 h as applicable. Data were appropriately pooled using random and mixed effects models. Our systematic review includes 56 studies reporting on a total of 7711 pediatric patients. A meta-analysis of the 10 eligible studies directly comparing BCP (n = 416) to CCP (n = 281) was also performed. There was no significant difference between the two groups with regard to cTnI and Lac at any measured time point, ATP levels after reperfusion, length of intensive care unit stay (WMD: -0.08, 95% CI -1.52 to 1.36), length of hospital stay (WMD: 0.13, 95% CI -0.85 to 1.12), and 30-day mortality (OR 1.11, 95% CI 0.43-2.88). Only cTnI levels at 4 h postoperatively were significantly lower with BCP (WMD: -1.62, 95% CI -2.07 to -1.18). Based on the available data, neither cardioplegia modality seems to be superior in terms of clinical outcomes, ischemia severity, and overall functional recovery.

Comparison of high glucose concentration blood and crystalloid cardioplegia in paediatric cardiac surgery: a randomized clinical trial

OBJECTIVES

This study investigates the effects of high glucose content on patients undergoing cold crystalloid versus cold blood cardioplegia in terms of early clinical results, functional myocardial recovery and ischaemia-reperfusion injury in patients undergoing repair of acyanotic cardiac lesions.

METHODS

Patients were randomly assigned to receive either crystalloid (n = 31) or blood cardioplegia (n = 31). Early clinical results were assessed. Changes in left ventricular fractional shortening, arterial blood lactate levels, central venous saturation, cardiac Troponin I release and blood glucose concentration were measured during the first 24 h after ischaemia.

RESULTS

There was no significant difference in clinical outcomes and postoperative complication rates between groups. The postoperative changes in left ventricular function, lactate levels, central venous saturation and Troponin I were not significantly different between groups. The use of crystalloid cardioplegia was associated with significant increases in serum glucose compared with blood cardioplegia.

CONCLUSIONS

A high glucose content blood cardioplegia does not show any advantage compared with crystalloid cardioplegia in terms of clinical outcomes, functional recovery and the degree of ischaemic injury in infants and children undergoing repair of acyanotic heart lesions. High glucose concentration of the cardioplegic solution might potentiate ischaemia-reperfusion injury and diminish the beneficial effects of blood cardioplegia.

Effect of esmolol on myocardial protection in pediatrics congenital heart defects

Background:

Although it is accepted that inducing cardioplegia is the gold standard in myocardial protection, there is still no consensus on the exact type of the cardioplegia. There are fewer studies on the type of the cardioplegia in hearts of the children than adults and they are contradictory. The effects of esmolol have been reviewed (a type of ultrashort-acting beta-adrenergic antagonist, i.e., ß-blockers) in conjunction with the cardioplegia due to the effect of the β-blockers in reducing the myocardial ischemia and reperfusion.

Materials and Methods:

The left ventricle ejection fraction (LVEF), systolic blood pressure, central venous pressure (CVP), heart rate, etc., were recorded separately in patients who received the cardioplegia without esmolol (n = 35) and with esmolol (n = 30) and matched for the age and sex.

Results:

The amount of inotrope used in the group without esmolol (100%) was considerably higher than in the group with esmolol (86.7%). Postoperative arrhythmias did not differ significantly between the two groups. There was no significant difference in the duration of cardiopulmonary bypass (CPB), time of the extubation, length of the ICU stay, the first day EF after surgery, and the first week EF after surgery as well. Creatinine kinase-MB (CKMB) was significantly higher in the group without esmolol during operation than in the group with esmolol.

Conclusions:

The patients who received cardioplegia along with esmolol had less inotropic requirement after operation, and increase in EF and cardiac output (CO) 1 week after surgery. In addition, it reduced damage to the heart during surgery, and patients may have greater stability in the cardiac conduction system.

Blood versus crystalloid cardioplegia for pediatric cardiac surgery: a meta-analysis

OBJECTIVE

Blood and crystalloid cardioplegia are the main myocardial protective solutions used in pediatric cardiac surgery. However, the effectiveness of these two solutions on myocardial metabolism, reperfusion injury and clinical outcomes in pediatric patients is still under debate. The purpose of this meta-analysis was to compare the efficacy of these two cardioplegia solutions in pediatric cardiac surgery.

METHODS

Keyword searches were performed on PUBMED, EMBASE and The Cochrane Library for randomized, controlled, clinical studies which were primarily comparing blood and crystalloid cardioplegia in pediatric cardiac surgery and provided data of postoperative cardiac troponin I (cTnI), lactate, mechanical ventilation time, length of intensive care unit (ICU) stay and inotropic support. Databases were searched from 1966 to June 2013 and were restricted to peer-reviewed English language publications of human subjects. We summarized the combined results of the data as mean difference (MD, when outcome measurements were made on the same scale) or standard mean difference (SMD, when the studies assess the same outcome with different scales), with 95% confidence intervals.

RESULTS

Five studies were identified, with a total of 323 patients. Lactate level after cardiopulmonary bypass (CPB) was significantly lower after blood cardioplegia compared with crystalloid cardioplegia (SMD 1.09, 95%CI 0.12 to 2.06, p=0.03); cTnI release postoperatively at 4-6 h (MD 0.92 ng/ml, 95%CI -0.13 to 1.97, p=0.09), 12 h (MD 0.2 ng/ml, 95% CI -0.43 to 0.84, p=0.53) and 24 h (MD 0.98 ng/ml, 95%CI -0.26 to 2.22, p=0.12) was not significantly different between the groups; ventilation duration (MD 5.15 hours, 95%CI -7.51 to 17.81, p=0.42) and length of ICU stay (SMD -0.3, 95%CI -0.80 to 0.21, p=0.25) were not significantly different between the groups either.

CONCLUSION

Myocardial metabolism was better in the blood cardioplegia group compared with the crystalloid cardioplegia group. However, there was no evidence of improvement in myocardial damage or clinical outcome for either cardioplegia solution.

Is there any difference between blood and crystalloid cardioplegia for myocardial protection during cardiac surgery? A meta-analysis of 5576 patients from 36 randomized trials

Objective:

To compare the efficacy of blood versus crystalloid cardioplegia for myocardial protection in patients undergoing cardiac surgery.

Methods:

MEDLINE, EMBASE, CENTRAL/CCTR, SciELO, LILACS, Google Scholar and reference lists of relevant articles were searched for clinical studies that reported in-hospital outcomes after blood or crystalloid cardioplegia for myocardial protection during cardiac surgery procedures from 1966 to 2011. The principal summary measures were risk ratio (RR) for blood compared to crystalloid cardioplegia with 95% Confidence Interval (CI) and P values (considered statistically significant when <0.05). The RRs were combined across studies using the DerSimonian-Laird random effects model and fixed effects model using the Mantel-Haenszel model - both models were weighted. The meta-analysis was completed using the software Comprehensive Meta-Analysis version 2 (Biostat Inc., Englewood, New Jersey).

Results:

Thirty-six studies (randomized trials) were identified and included a total of 5576 patients (2834 for blood and 2742 for crystalloid). There was no significant difference between the blood and crystalloid groups in the risk for death (risk ratio [RR] 0.951, 95% CI 0.598 to 1.514, P=0.828, for both effect models) or myocardial infarction (RR 0.795, 95% CI 0.547 to 1.118, P=0.164, for both effect models) or low cardiac output syndrome (RR 0.765, 95% CI 0.580 to 1.142, P=0.094, for the fixed effect model; RR 0.690, 95% CI 0.480 to 1.042, P=0.072, for the random effect model). It was observed that there was no publication bias or heterogeneity of effects about any outcome.

Conclusion:

We found evidence that argues against any superiority in terms of hard outcomes between blood or crystalloid cardioplegia for myocardial protection during cardiac surgery.

Cold blood cardioplegia reduces the increase in cardiac enzyme levels compared with cold crystalloid cardioplegia in patients undergoing aortic valve replacement for isolated aortic stenosis

OBJECTIVES

Cardiac arrest during cardiac surgery is most commonly induced by cold blood or cold crystalloid cardioplegia. The results from clinical studies are divergent regarding which of the 2 solutions provides better myocardial protection. This might be explained by several factors. Both heterogeneity in disease for the included patients and the fact that most studies are retrospective in design and that patients with coronary artery disease with different degrees of myocardial ischemia are included might explain these findings. To circumvent these potentially confounding factors, we included in a prospective randomized study only patients undergoing aortic valve replacement for aortic stenosis without other significant cardiac disease. Patients were randomized to antegrade cold crystalloid or cold blood cardioplegia.

METHODS

Eighty patients with aortic stenosis undergoing aortic valve replacement without significant coronary artery stenosis or other significant concomitant heart valve disease were included in the study. They were randomized to either antegrade cold blood or cold crystalloid cardioplegic solution delivered through the coronary ostia every 20 minutes throughout the period of aortic crossclamping. Maximum postoperative creatine kinase isoenzyme MB and troponin-T levels, well-established markers of myocardial damage, were compared between the 2 groups.

RESULTS

Both maximum postoperative creatine kinase isoenzyme MB and troponin-T levels were significantly higher by approximately 100% in the cohort of patients receiving crystalloid compared with blood cardioplegia. Only in the group of patients receiving cold crystalloid cardioplegia was there a positive correlation between cardiac enzyme levels and crossclamp time.

CONCLUSION

Antegrade cold blood cardioplegia provides better myocardial protection than cold crystalloid cardioplegia in patients undergoing aortic valve replacement.

Myocardial substrates in children with congenital heart disease: relationship to substrate supply, age, growth and desaturation

AIM

The myocardial uptake of substrates in children has only been investigated on a small scale. The purpose of this study was to define myocardial substrate uptake in relation to the arterial supply of substrates, age, growth and oxygen saturation.

METHODS

Thirty patients with congenital heart disease, aged 3 months to 16 years, were studied during cardiac catheterization. Arterial and coronary sinus blood was analyzed for the major fuel metabolites and amino acids.

RESULTS

The uptake of all major substrates correlated significantly with the arterial supply: free fatty acids (r = 0.52, p = 0.004), beta-hydroxybutyrate (r = 0.74, p < 0.0001), lactate (r = 0.70, p < 0.0001) and glucose (r = 0.48, p = 0.01). Free fatty acids were the dominant substrate, irrespective of age, growth and saturation. With age, there was an increase in the uptake of lactate (r = 0.61, p = 0.0004) and a decrease in the uptake of beta-hydroxybutyrate (r =-0.41, p = 0.02). In multivariate analyses, these changes were explained by the arterial supply of the substrates, while age per se did not contribute significantly.

CONCLUSION

The uptake of myocardial metabolites correlated with the arterial supply. Free fatty acids were the dominant substrate at all ages. The uptake of lactate and beta-hydroxybutyrate, although varying with age, was also determined by the arterial supply.

Intermittent warm blood cardioplegia in the surgical treatment of congenital heart disease: Clinical experience with 1400 cases

OBJECTIVE

To analyze our experience with warm blood cardioplegia in pediatric cardiac surgery.

METHODS

We used intermittent (every 15 minutes after initial injection) warm blood cardioplegia in the treatment of 1400 patients. Results were retrospectively compared with those of 950 patients treated with cold blood cardioplegia. The following parameters were analyzed: (1) hydric balance of cardioplegic solution; (2) resumption of rhythm after aortic crossclamp removal; (3) duration of mechanical ventilation, intensive care unit stay, and incidence of mortality in 4 selected diagnostic groups: ventricular septal defect, tetralogy of Fallot, atrioventricular septal defect, and transposition of the great arteries. These 4 groups, treated with warm or cold cardioplegia, were comparable with regard to age, weight, crossclamp times, and percent with Down syndrome; (4) troponin level at 12 hours after aortic crossclamping; and (5) duration of intensive care unit stay for the 1400 patients.

RESULTS

Warm versus cold cardioplegia: negligible fluid addition with warm cardioplegia compared with blood loss/prime dilution induced by cold cardioplegia; spontaneous resumption of sinus rhythm in 99% versus 77% of patients (P < .001); shorter duration of ventilatory support in each diagnostic group, significant in all cases; smaller increase in troponin in each group (P < .05). Incidence of early death was not different in the 2 groups. For the whole group, duration of the intensive care unit stay was less than 48 hours in 86% versus 75% (P < .001).

CONCLUSION

In our experience, normothermic cardioplegia has not generated any particular inconvenience and its use was contemporary, with improved outcomes.

Myocardial Metabolism is Better Preserved After Blood Cardioplegia in Infants

BACKGROUND

We have previously reported improved hemodynamic function after blood cardioplegia in comparison with crystalloid cardioplegia. Furthermore, lactate was released from the heart after crystalloid cardioplegia but not after blood cardioplegia. The purpose of this study was to determine whether the difference in substrate metabolism between the two cardioplegia methods was restricted to lactate, or whether the difference in metabolic derangement was more extensive.

METHODS

Thirty consecutive infants with complete atrioventricular septal defects were included in this prospective, randomized, controlled study. Arterial and coronary sinus blood concentrations of substrates and amino acids were measured after weaning from bypass.

RESULTS

After crystalloid cardioplegia, there was a myocardial uptake of glutamate (p = 0.003), leucine (p = 0.03), lysine (p = 0.003), and beta-hydroxybutyrate (p = 0.004), whereas lactate was released (p = 0.03). After blood cardioplegia, there was a myocardial uptake of free fatty acids (p = 0.01) but no uptake of amino acids and no release of lactate.

CONCLUSIONS

There are differences in myocardial substrate metabolism between blood cardioplegia and crystalloid cardioplegia, which involve carbohydrates and amino acids. The differences may include lipids but our data in this respect are not conclusive.

Blood Cardioplegia Provides Superior Protection in Infant Cardiac Surgery

BACKGROUND

We hypothesized that blood cardioplegia preserves myocardial metabolism and function more effectively than St Thomas' crystalloid cardioplegia in infant cardiac surgery.

METHODS

Thirty infants with atrioventricular septal defects were randomly allocated to either blood or crystalloid intermittent cold (4 degrees C) cardioplegia. Arterial and coronary sinus blood was analyzed for lactate and oxygen. Cardiac output (thermodilution) and left ventricular function (echocardiography) were evaluated.

RESULTS

The lactate concentration in coronary sinus blood early after bypass was significantly higher after crystalloid cardioplegia than after blood cardioplegia (2.1 +/- 0.3 vs 1.3 +/- 0.1 mmol/L, p = 0.006), with a significant myocardial release of lactate after crystalloid but not after blood cardioplegia. Oxygen extraction (arterial-coronary sinus O2 content) was higher early after crystalloid cardioplegia (3.02 +/- 0.13 vs 2.35 +/- 0.22 mmol/L, p = 0.01), possibly reflecting a difference in oxygen debt. The cardiac index was higher after blood cardioplegia (4.9 +/- 0.3 vs 4.0 +/- 0.3 L/min(-1)/m(-2), p = 0.04) and echocardiographic grading of left ventricular function was better (4.1 +/- 0.17 vs 3.5 +/- 0.22 arbitrary units, p = 0.046).

CONCLUSIONS

This study indicates that blood cardioplegia preserves myocardial metabolism and function more effectively than crystalloid cardioplegia in infant cardiac surgery. The clinical significance of this finding is uncertain, but the more than 20% increase in cardiac index in the critical phase during weaning from bypass may be advantageous.

Myocardial protection in congenital heart surgery

Modern pediatric cardiac surgery prides itself by performing primary surgical repair of cardiac anomalies. As a consequence, the majority of cases are nowadays performed in neonates and young infants. For the repair of intracardiac malformations the aorta is crossclamped and the heart is arrested (i.e. subjected to ischemia). Cardioplegic solution is administered routinely to arrest the contractile apparatus, decrease energy consumption and thereby increase ischemia tolerance. It is usually combined with hypothermia as another method to extend ischemia tolerance. In pediatric cardiac surgery several different cardioplegic solutions and strategies are currently used. For myocardial protection during crossclamp time either blood or crystalloid solution is administered into the aortic root or retrogradely into the coronary sinus, intermittently or as a single shot. The final concept for myocardial protection is highly dependent on the individual surgeon and his personal preference. There is currently no evidence in favor of one or the other technique. Thus, pediatric protection is currently experience-based.

Cold blood cardioplegia versus cold crystalloid cardioplegia: A prospective randomized study of 1440 patients undergoing coronary artery bypass grafting

OBJECTIVES

A large number of experimental studies have indicated that blood cardioplegia might be superior to crystalloid cardioplegia for myocardial protection during ischemic arrest. However, no prospectively randomized studies of large patient series have been undertaken to prove potential differences in clinical course.

METHODS

Over a 52-month period, all patients undergoing on-pump coronary artery bypass operated on by 2 surgeons were prospectively randomized to receive either cold crystalloid cardioplegia (group C) or cold blood cardioplegia (group B) during aortic crossclamping.

RESULTS

Altogether, 1440 patients aged 37 to 89 years (median, 66 years) entered the study (group C, n = 719; group B, n = 721). The groups were comparable in all major demographic, preoperative, and operative variables. The clinical course turned out to be nearly identical for both groups. No statistically significant differences were seen concerning spontaneous sinus rhythm after aortic declamping, use of inotropic drugs or intra-aortic balloon pumping, postoperative ventilatory support, bleeding and rate of allogeneic blood transfusions, perioperative myocardial infarction, episodes of atrial fibrillation, stroke or minor neurologic dysfunction, renal function, infections, physical rehabilitation, or mortality. Also, in subgroups of patients at higher operative risk (female sex, age >70 years, unstable angina, diabetes, emergency operation, ejection fraction <0.50, crossclamping time >50 minutes, and EuroSCORE >4), no statistically significant differences could be demonstrated between the groups.

CONCLUSIONS

There were no significant differences whether myocardial protection was performed with cold blood cardioplegia or cold crystalloid cardioplegia during aortic crossclamping in patients undergoing coronary artery bypass grafting. The extra costs related to blood cardioplegia might be saved.

Myocardial metabolic changes during pediatric cardiac surgery: a randomized study of 3 cardioplegic techniques

BACKGROUND

Blood cardioplegia and terminal warm blood cardioplegic reperfusion ("hot shot") reduce myocardial injury and improve metabolic recovery in hypoxic but not normoxic experimental models. However, there is little evidence of a benefit of either technique in pediatric clinical practice compared with crystalloid cardioplegia.

METHODS

Pediatric patients undergoing cardiac surgery were randomized to receive intermittent antegrade cold crystalloid cardioplegia, cold blood cardioplegia, or cold blood cardioplegia with a hot shot. Right ventricular biopsy specimens were collected before ischemia, at the end of ischemia, and 20 minutes after reperfusion. Cellular metabolites were analyzed. In acyanotic patients postoperative serum troponin I levels were also measured at 1, 4, 12, 24, and 48 hours.

RESULTS

Of 103 patients recruited, 32 (22 acyanotic and 10 cyanotic), 36 (24 acyanotic and 12 cyanotic), and 35 (25 acyanotic and 10 cyanotic), respectively, were allocated to the groups receiving cold crystalloid cardioplegia, cold blood cardioplegia, and cold blood cardioplegia with a hot shot. Cyanotic patients were younger, with longer crossclamp times. There were no significant differences in clinical outcomes between cardioplegic methods. The cardioplegic method had no overall effect in terms of adenosine triphosphate, ln(adenosine triphosphate/adenosine diphosphate), or ln(glutamate) in acyanotic patients (P =.11, P =.66, and P =.30, respectively). Also, there was no significant difference between groups in troponin I release. However, in cyanotic patients cold blood cardioplegia with a hot shot significantly reduced the decrease in adenosine triphosphate, ln(adenosine triphosphate/adenosine diphosphate), and glutamate observed at the end of ischemia and after reperfusion compared with the decrease seen in those receiving cold crystalloid cardioplegia (P =.002, P =.003, and P =.008, respectively), with cold blood cardioplegia representing an intermediate.

CONCLUSIONS

For cyanotic patients (younger, with longer crossclamp times), cold blood cardioplegia with a hot shot is the best method of myocardial protection. For acyanotic patients (older, with shorter crossclamp times), cardioplegic technique is not critical.

Cardioplegia in pediatric cardiac surgery: do we believe in magic?

Cardioplegia has become the gold standard of myocardial protection for practically every type of heart surgery during which the ascending aorta must be clamped. Although there is little doubt about the efficacy of cardioplegia in the adult heart, there are few studies on the pediatric heart and their results are contradictory. The physiology of pediatric heart muscle differs considerably from that of the adult myocardium. The pediatric heart distinguishes itself from that of the adult most impressively in its greater tolerance for ischemia. This ischemia tolerance is enhanced by the use of hypothermia. Considering that hypothermia is a powerful tool to prolong ischemia tolerance and that most pediatric cardiac surgeons report similar results using different types of cardioplegia, some surgeons are tempted to suspect that the contribution of the cardioplegia composition to protecting the pediatric heart may be overestimated. This provocative statement is critically discussed in this article. We examine the protective potential of cardioplegia (in various compositions), or of hypothermia, or of both in pediatric cardiac surgery. We pay special attention to several key differences between the physiologies of the pediatric myocardium and the adult myocardium and attempt to relate them to the available surgical methods of myocardial protection. We conclude that the composition of cardioplegia indeed is an important component of successful operative management in pediatric heart surgery. We provide evidence that the benefit of cardioplegia over hypothermia alone is minor at low temperatures (below 15 degrees C), but becomes substantial when the temperature increases.

Cold blood versus cold crystalloid cardioplegia for repair of ventricular septal defects in pediatric heart surgery: a randomized controlled trial

BACKGROUND

There is little evidence in the literature on the benefits of cold blood cardioplegia in pediatric cardiac surgery. This study investigates the effects of cold crystalloid versus cold blood cardioplegia on myocardial metabolism, reperfusion injury, and clinical outcomes in patients undergoing ventricular septal defect (VSD) repair.

METHODS

Patients were randomly assigned to receive antegrade cold (4 to 6 degrees C) St Thomas's I crystalloid (CCC) or blood (CBC) cardioplegia. Changes in myocardial adenine nucleotides and purine levels were monitored in right ventricular biopsies and postoperative serum troponin I (TnI) and lactate release were measured.

RESULTS

Forty patients were randomly assigned to CCC (n = 21; age 21.1 +/- 40.8 months) or to CBC (n = 19; age 27.4 +/- 39.3 months). Patient characteristics were similar in the two groups and there was no mortality. After the ischemic period there was a significant drop in adenosine triphosphate levels compared with control values in the CCC (40.4 +/- 9.9 versus 27.5 +/- 12.5 nmol/mg protein, p = 0.01) but not in the CBC group (40.3 +/- 23.2 versus 37.3 +/- 18.9 nmol/mg protein). The fall was more marked in infants compared with children (40% versus 10%, respectively, p = 0.01). Mean total TnI release was 42% lower in the CBC than the CBC group (95% confidence interval 10% to 62%, p = 0.015). Total TnI release was significantly associated with age (p < 0.001) but as levels in infants in the CBC group were the same as for children, the reduction with age was seen almost entirely in the CCC group. There were no differences in the duration of inotropic support, ventilation time, intensive care unit, or hospital stay in the two groups.

CONCLUSION

The use of CBC is associated with less metabolic myocardial ischemic stress and reperfusion injury when compared with CCC in pediatric patients undergoing VSD repair.

Effects of chlorpromazine as a systemic vasodilator during cardiopulmonary bypass in neonates

OBJECTIVES

Vasodilator use during cardiopulmonary bypass is important in pediatric cardiac surgery, but the full range of their effects on hemodynamics remains to be clarified. We studied the effects of chlorpromazine, a potent alpha-blocking agent, in neonates.

METHODS

Subjects were 60 neonates undergoing arterial switch operations for complete transposition of the great arteries with an intact ventricular septum. Of these, 37 received 2.1 to 6.5 mg/kg of chlorpromazine during cardiopulmonary bypass (CPZ group) and 23 received no vasodilator (control group). We then compared hemodynamic parameters between groups during and early after surgery.

RESULTS

The systemic vascular resistance index and mean arterial pressure during cardiopulmonary bypass were significantly lower in the CPZ group (p < 0.05), but systolic pressure 15 minutes after cessation of cardiopulmonary bypass did not differ between groups. The rise in peripheral temperature during rewarming after hypothermia was significantly higher and the acid-base status 40 minutes after cardiopulmonary bypass less acidotic in the CPZ group. Urine output during cardiopulmonary bypass was higher in the CPZ group.

CONCLUSIONS

Chlorpromazine effectively counteracts systemic vasoconstriction induced by cardiopulmonary bypass without serious side effects in neonatal cardiac surgery.

Age-dependent and hypoxia-related differences in myocardial protection during pediatric open heart surgery

BACKGROUND

Current cardioplegic protection techniques used in pediatric cardiac surgery do not take into consideration age and cyanotic differences. The aim of the present work was to address this question by monitoring clinical outcome, myocardial metabolism, and reperfusion injury in pediatric patients protected by cold-crystalloid cardioplegia.

METHODS AND RESULTS

Fifty-eight patients (31 children and 27 infants) with or without hypoxic stress (cyanosis) undergoing open heart surgery with cold-crystalloid cardioplegia were included in the study. Clinical outcome measures assessed included inotropic and ventilatory support, intensive care, and hospital stay. Ischemia-induced changes in metabolism (adenine nucleotides, purines, lactate, and amino acids) were determined in ventricular biopsies collected at the beginning and end of ischemic time (cross-clamp time). Reperfusion injury was assessed by measuring postoperative serial release of troponin I. Evidence was observed of ischemic stress during cardioplegic arrest in children and infants as shown by significant changes in cellular metabolites. Compared with infants, children had significantly less reperfusion injury and better clinical outcome, and these factors were related to duration of ischemic time. Cyanosis did not influence outcome in infants, but cyanotic children showed worse reperfusion injury and clinical outcome than acyanotic children.

CONCLUSIONS

Extent of myocardial protection with cold-crystalloid cardioplegia in pediatric open heart surgery is dependent on age and degree of cyanosis.

Effects of retrograde cardioplegia on myocardial perfusion and energy metabolism in immature porcine myocardium

OBJECTIVES

Retrograde cardioplegia has been widely used for the protection of adult hearts during cardiac operations. Its efficacy to protect immature myocardium is still unclear. This study was designed to assess the effects of retrograde cardioplegia on myocardial perfusion and energy metabolism in immature hearts.

METHODS

Piglet hearts were divided into 3 groups. Hearts in group 1 were used to assess myocardial perfusion of retrograde cardioplegia by means of magnetic resonance imaging. Hearts in groups 2 and 3 were used to assess the effects of retrograde cardioplegia on myocardial energy metabolism by use of phosphorus 31 magnetic resonance spectroscopy.

RESULTS

Magnetic resonance images showed that perfusion with retrograde cardioplegic solution was heterogeneous. A perfusion defect was noted during retrograde cardioplegia in the right ventricular wall and in a portion of the posterior wall of the left ventricle in 4 of 6 hearts. Phosphorus 31 spectra showed that at the end of 45-minute retrograde cardioplegia, myocardial intracellular pH was 6.83 +/- 0.17 and phosphocreatine was 53.5% +/- 27% of its prearrest value. The adenosine triphosphate level, however, remained normal throughout the retrograde cardioplegia period. Last, the hearts subjected to retrograde cardioplegia or antegrade cardioplegia showed similar and complete metabolic and functional recovery during reperfusion.

CONCLUSIONS

Retrograde cardioplegia provides heterogeneous perfusion. Its ability to protect the right ventricular myocardium is poor and varies between individuals. Myocardial perfusion provided by retrograde cardioplegia is slightly less than that needed to sustain normal myocardial energy metabolism under normothermic conditions.

Effect of partial oxygen supply on mitochondrial electron transport system during complete cardiac ischemia

During complete ischemia we assessed myocardial utilization of the small amount of oxygen available. We also determined whether blood cardioplegia has any advantage over crystalloid cardioplegia in this setting. Patients with preserved left ventricular myocardial function and without anterolateral wall infarct or aneurysm were included to the study. Intermittent cold blood and crystalloid cardioplegia were used in 10 patients (group BC) and 9 patients (group CC), respectively. From myocardial biopsies, obtained before and after ischemia, complete electron transport system (ETS) enzyme activities (NDH, SDH, NCCR, SCCR, and COX) and lactate content were analyzed. Biochemical and hemodynamic analyses also were done. Myocardial and blood temperatures were monitored. Ischemic time was longer in group CC (p < 0.05). There were no important differences in biochemical and hemodynamic variables between the two groups. In addition, there was no difference in NDH and SDH activities as well as COX/SCCR and COX/RS-NCCR ratios between the two groups before and after ischemia. After Ischemia, RS-NCCR in group CC and SCCR and COX activities in both groups were lower than the control. For all enzymes, activity change ratios were not different between groups. Myocardial lactate content was increased in both groups after ischemia. However, the increase in group BC was less (p < 0.01). Based on our findings, we believe that the superiority of blood cardioplegia over crystalloid cardioplegia does not depend on oxygen content, but on other factors such as buffering and free oxygen radical scavenger effects among others. However, with the warm and continuous blood cardioplegia technique, oxygen content might be more important.